SHANGHAI (Reuters) - China's domestically developed C919 passenger jet is likely to make its third test flight within days or in up to two weeks, a senior Commercial Aircraft Corp of China Ltd (COMAC) [CMAFC.UL] executive told reporters on Friday.

The narrow-body C919, which will compete with Boeing Co's <BA.N> 737 and the Airbus SE <AIR.PA> A320, completed its second test flight on Thursday, almost five months after its maiden flight earlier this year in May.

Shi Jianzhong, COMAC Vice President, said a number of "issues" relating to the plane's technology and its engine had led to the lengthy gap between the C919's first and second flight.

"We were being cautious," he said, speaking at an event to announce the naming of a separate wide-body jet being developed by COMAC and Russia's United Aircraft Corporation (UAC), which will be called the CR929.

"We expect future test flights to be very close together," he said, adding that the next flight could be "a few days or one to two weeks" away.

The almost five month-gap between the C919's first and second flight was far longer than that of other planes, such as the Airbus A350 whose gap was five days.

On the CR929, UAC said in a statement that the team had already decided on the plane's family concept and its preliminary characteristics. Shi said that the plane was in the second, design-focused, stage of its development.

The two companies' joint venture, which was set up in May, will be called China-Russia Commercial Aircraft International Corporation (CRAIC), they said.